A comprehensive method for multipath performance analysis of GNSS navigation signals

Multipath error is the most important unavoidable source of error contributing to the User Equivalent Range Error (UERE). It is difficult to model, but it is very necessary for us to describe signal multipath performance of Global Navigation Satellite System (GNSS). Multipath error envelope based on noncoherent early-late code tracking loop has become a common approach to describe the effects of specular multipath, which is widely used in navigation signal performance evaluation. A more practical and reliable way for multipath performance assessment is the computation of the running average of multipath error envelope. For this purpose, only the absolute envelope values are considered and their cumulative sum is used to compute the running average for the multipath error envelope. The mean value of the absolute values of the in-phase and the anti-phase shift component of the multipath error envelopes has been used to compute the running average of an envelope. Considering the numerical method can not reveal the direct relation between the navigation signal and multipath error envelope for the assessment of the navigation signal, theoretical approximation explicit expression for multipath error envelope is derived through first order Taylor expansion. The explicit expression method has its limitations. The computation of multipath error envelopes is based on the assumptions that the direct signal component is always available and no shadowing effects, only one multipath signal is obtained and the multipath signal undergoes specific amplitude attenuation relative to the direct signal. Furthermore, a static environment is assumed. To overcome these limitations and get a more realistic view on the actual multipath performance, a simple model that considers statistical distributions of geometric path delays and multipath relative amplitudes is introduced, allowing the computation of weighted multipath error envelopes which are valid for different multipath environments such as open, rural, suburban and urban scenarios. The paper aims at deriving multipath error envelope explicit expression from simplified and practical statistical channel model with considering open, rural, suburban and urban scenarios. The results indicate that the comprehensive method is effective. This multipath error envelope analytical method may be used in future navigation signal design.